In Fig. 69 is shown a 2,000 brake-horse-power horizontal M.A.N. Diesel engine of the four stroke cycle type which is installed at the Halle Municipal Electricity Works, Halle, Germany. It is of the double acting type with twin-tandem cylinders giving four working impulses per revolution. This engine was installed in addition to the six producer gas engines already in place to take the peak load of the station at different times during the day, the gas engines meeting the normal steady demand. This firm has built many thousands of the vertical type of Diesel engine of all sizes, and has recently installed 13 engines of 4,500 brake horse-power for operating the Kreff tramways. The company is now building cylinders giving outputs of from 1,200 to 1,500 brake horse-power per cylinder, giving outputs of from 5,000 to 6,000 horse-power in tandem twin type engines. As will be seen from the cut, the horizontal Diesel engine is remarkably free from complicated valve gear. (65) Mirlees-Diesel Engines. The Mirlees-Diesel engine is built by the English firm, Mirlees, Bickerton and Day both for stationary and marine service. A generating plant consisting of two, 200 horse-power Mirlees engines direct connected to Siemens generators has been installed in the municipal plant at Dundalk as shown by Fig. 71. On test these units consumed 0.647 pounds of oil per horse-power at full load and 0.704 pounds per horse-power at half load with a regulation of 3.24 per cent from full load to no load. All of the engines built by this firm are of the four stroke cycle type. [Illustration: Fig. 71. Mirlees-Diesels at Dundalk. ] (66) Willans-Diesel Engines. The Willans-Diesel engines built by the Willans and Robinson Company of Rugby, England, are in sizes up to 400 brake horsepower, and run at speeds up to 250 revolutions per minute. They are all of the four stroke cycle type and are applied principally to the driving of electric generators. The cut shows one of the four, 280 horse-power units supplied to the Alranza Company and the Rosario Nitrate Works in South America. [Illustration: Fig. 72. Willans Vertical Diesel Engine. ] Unlike the Mirlees engine, the Willans has an individual frame for each cylinder as in steam engine practice. Like the steam engine frame, the bottom is left open for the inspection of the connecting rod ends and the main bearings which is a most desirable feature. The air compressor and pumps are arranged in a most compact form at the left end of the crank-shaft from which the pipes may be seen issuing to the four cylinders. The valves and over head gear are of the conventional type, which, with the exception of a few minor details are the same as those on the recently developed Sulzer-Diesel. The individual grouping of the cylinder units has many desirable features and should, we believe, be more extensively copied. (67) Installation and Consumption of Diesel Plant.